Infants born prematurely (known as "premature infants") are often extremely fragile and require specialized medical care. An important concern of such medical care is the condition of the infant's respiratory system, which is one of the last organs to fully develop in an infant before birth. Deprivation of oxygen caused by a premature infant's underdeveloped respiratory system can have serious consequences.
Instruments, such as pulse oximeters, are commonly used to identify problems with a patient's respiratory system. The color of the blood (i.e., the amounts of red and infrared radiation absorbed by the blood) is a function of the oxygen saturation of the heme in the blood's hemoglobin. For example, heme that is saturated with oxygen appears bright red because saturated heme is highly permeable to red light. In contrast, heme that is deoxygenated appears dark and bluish as it is less permeable to red light. A pulse oximeter measures the oxygen saturation of arterial blood by irradiating the blood with red and infrared radiation generated by one or more emitters, receiving the unabsorbed radiation with a detector, and, based on the unabsorbed radiation component, determining the corresponding amounts of the red and infrared radiation that are absorbed by the heme in the blood.
There are a number of competing design considerations for pulse oximeters, particularly when the oximeters are to be applied to premature infants. First, the pulse oximeters should have the ability to achieve a reliable interface between the emitter and detector in the sensor and the patient's skin. This is particularly a challenge when the oximeter is applied to premature infants due to the small size of the infants at birth. Second, the pulse oximeter should be adapted for ready application and removal from the patient with a minimal amount of pair or discomfort for the patient. Finally, the pulse oximeter should provide, particularly in the case of premature infants, a gentle interface with the patient's skin. As will be appreciated, the gelatinous skin and other tissue of premature infants is typically not fully developed and therefore can be extremely fragile.